Corporate America is now leading the way in extending benefits to lesbian, gay, bisexual and transgender employees. This quiet revolution has taken place even though it is legal in 29 states, including Texas, to discriminate against employees because of their sexual orientation.

The 2012 report by the Human Rights Campaign Foundation, which is the research and education arm of the LGBT civil rights group, reveals a rather remarkable transformation over the last decade. An astonishing 88 of the Fortune 500 companies received perfect scores in the annual Corporate Equality Index, which was even more rigorous this time around because the top rating required employers to extend health insurance coverage without exclusions to transgender employees.

Indeed, a large majority of Fortune 500 companies scored very well because they forbid discrimination based on sexual orientation. If you are an LGBT employee at AT&T, Dell Inc. or AMR Corp. — the three local Fortune 500 companies that received the highest rating possible — the anti-discrimination policies legally protect you where Texas explicitly does not.

The one glaring exception to this positive trend remains Irving-based ExxonMobil. It is the only company to get a negative rating in the index, out of 636 that were scored, including all those on the Fortune 500 list. By comparison, half of the companies in the top 20 of the Fortune 500 list received perfect scores, Chevron among them.

It wasn’t always this way. Before the merger in 1999, Mobil was a pioneer on the equality front. The company included sexual orientation in its nondiscrimination policy and even offered domestic-partner benefits. After the merger, Exxon changed the policy, though benefits were grandfathered for Mobil employees who had been receiving them.

ExxonMobil this year again asked the Securities and Exchange Commission to allow it to omit a resolution on sexual orientation from its shareholder meeting here next Wednesday, arguing, as it has in the past, that its current anti-discrimination policies are sufficient. The company also points out that support for the resolution dropped last year after reaching almost 40 percent in 2008 and 2009.

The SEC declined the request, which means the nonbinding resolution again will be put to a vote. The prime sponsor again is New York state comptroller Thomas P. DiNapoli, a trustee of the $147.2 billion New York state pension fund. DiNapoli over the past three years has managed to get 27 companies to adopt new nondiscrimination policies. His sound argument is that companies that extend protection to all employees have a competitive advantage in drawing workers and mitigate their risk of litigation.

ExxonMobil, the largest publicly traded oil and gas company in the world, should heed the call this time around. By explicitly prohibiting discrimination based on sexual orientation, the company will join the growing community of corporations that now view this as an essential and even indispensable part of doing business.

Texas companies rate well

Companies that rate 80 or higher in the Human Rights Campaign Foundation’s index earn the green designation, which is awarded to those that receive the highest workplace equality scores. All those rated are on the Fortune 1000 list.